As a conventional example, Document 1 (JP 2009-182097 A) describes a power supply apparatus (lighting apparatus) for driving LEDs. In the conventional example, a direct-current voltage supplied from a secondary battery (storage battery) is stepped up and is then output to an LED unit (illumination load) so as to turn on the LED unit. Moreover, in the conventional example, a battery voltage of the secondary battery is monitored, and if the battery voltage is within a normal range, an output current led to the LED unit is subjected to constant current control. Alternatively, if the battery voltage falls below the normal range, the output current led to the LED unit is reduced.
In the lighting apparatus of the conventional example, when the battery voltage (input voltage) varies in a short cycle, the output current also varies in a short cycle in accordance with the battery voltage. When the output current of the lighting apparatus varies in a short cycle, the quantity of light of the LED unit may also vary in a short cycle, which may cause flickering.